Diversity

Swifts are in the order Apodiformes, suborder Apodi and family Apodidae. There are two subfamilies of swifts: 13 species of Cypseloidinae (primitive American swifts) and 79 species of Apodinae (swiftlets, spinetails and typical swifts). The subfamily Apodinae is divided in to three tribes: 28 species of Collocaliini (swiftlets), 24 species of Chaeturini (spinetails) and 27 species of Apodini (typical swifts). The tribe Chaeturini is sometimes listed as its own subfamily Chaeturinae. There are 19 genera of swifts and a total of 92 species.

Swifts are very aerial species and spend much of their lives on the wing. Their sickle-shaped wings are well adapted for high-speed flight. As their name Apodidae (meaning “without feet”) suggests, they have tiny feet and are not able to perch. However, modified tail feathers help swifts land on and move around on vertical surfaces. Their plumage is dull black or brown; some species have white or gray patches, and a few have brighter chestnut-reddish throats. Males and females look similar and both play equal roles in nesting and rearing young.

Many swifts nest in caves, on cliffs or in hollows of dead trees. They often use saliva as glue to hold their nests together and to attach them to the substrate. The nests of edible-nest swiftlets (Aerodramus fuciphagus) are a delicacy in some parts of the world and are used to make bird nest soup. (Chantler and Driessens, 2000; Chantler, 1999; )

Geographic Range

Swifts are a cosmopolitan family; they are found on all continents except Antarctica and are common throughout the Neotropical, Nearctic, Oriental, Ethiopian, Australian and Palearctic regions. (Campbell and Lack, 1985; Chantler, 1999; Collins, 2001; )

Habitat

Swifts are terrestrial species that require foraging habitat with high numbers of aerial insects. They are found in virtually any temperate or tropical area where prey can be found. Swift habitat includes desert oasis, Mediterranean scrub, steppe, farm or grassland, urban areas, forest and canyons. They can be found from sea level to 4000 m. Because water is an integral aspect of the breeding biology of many species, swifts are usually found near water.

Physical Description

Swifts are small birds (9-25 cm) usually with black or brown plumage. Some species have white on the throat or rump areas and a few species have brighter chestnut or reddish throats. Males and females are monomorphic (look alike) and are capable of high-speed flight. Swifts feed on the wing, and their large gape enables them to catch insects while in flight. Their long, narrow primary feathers and short secondary feathers allow for rapid flight and gliding; because they glide, swifts have small breast muscles relative to other similarly sized birds. Many species have hard tail-feathers with spiny tips to help brace against the walls of their roosting sites.

All swifts have short legs and tiny feet with sharp, curved claws; they cannot perch, but they are able to cling to vertical surfaces such as the cliffs and cave walls that serve as roosting sites. Because swifts use saliva to bind nesting material and attach nests to vertical surfaces, they have large salivary glands that increase in size during the breeding season. Swifts have feathering in front of their eyes; the feathers are thought to reduce glare and protect the eyes. Most species molt after they reach their wintering grounds, although some molt during the breeding season or just prior to migration.

Reproduction

Swifts are monogamous and males and females share equally in nesting and rearing young. In some tropical species pairs will stay together year-round. In other species new pair bonds are formed each year. Nest sites are defended by the nesting pair and fights over nesting sites can last for several hours. Males perform aerial displays and there have been reports of aerial copulation, but no confirmed observations. Mating normally occurs at the nest.

Breeding in swifts usually coincides with periods of high insect abundance. In the tropics swifts breed during the wet season. In temperate zones breeding occurs in the summer. Swifts living near the equator can breed year-round. Swifts living in areas with long breeding seasons can have two clutches, while those in areas with a short window of time for breeding will have only one. Most swifts are colonial breeders, though some are solitary. Nest sites are usually in dark places such as caves or hollow trees (Vaux’s swifts (Chaetura vauxi) will nest in the cavities made by pileated woodpeckers (Dryocopus pileatus)). Many species of swift have adapted to the human-modified landscape and will nest in man-made structures such as chimneys and under eves of buildings.

Swifts are unique in that they use saliva to glue together nest material and attach their nests to the substrate. Some even use saliva to glue their eggs to the nest. Nests are constructed of a variety of materials: moss, liverwort, feathers and branches. The nests of some swiftlets (Collocaliini) are made entirely of saliva. Cypseloidine swifts build nests with moss and lichen on ledges near or behind waterfalls and will sometimes re-use nests. Clutch size in these species is usually one. Chaeturine swifts build nests out of twigs and use saliva to hold the nest together and glue it to the nesting substrate. Clutch size in these species can be 4 to 5. Apodinae swifts build nests of plant material and feathers on crevices usually on cliffs, but also man-made structures. They are usually colonial nesters; clutch size ranges from 1 to 7, but is commonly 2 to 3. As is common for many colonially nesting species, nest parasites can be plentiful.

Swifts usually begin breeding during their second year. Clutch size varies depending on food quality and availability. Eggs are dull white and range in size from 15.5 by 10 mm to 43 by 28.5 mm. The egg-laying interval is every other day. Hatching is synchronous and incubation lasts from 14 to 32 days. After hatching, the altricial nestlings are brooded for 1 to 2 weeks depending on the weather.

Both swift eggs and nestlings are resistant to cooling, young swifts can go into torpor to conserve energy in cold weather. The weather also has a huge effect on nestling growth since feeding frequency depends on adult foraging success, which in turn depends on the weather. Young swifts have large fat stores and can therefore survive for long periods without being fed.

The nestling period lasts 5 to 8 weeks. This is longer than most similarly-sized birds because the nesting period is extended if food abundance is low. Before fledging, young swifts will perform “wing exercises” as they prepare for their life on the wing. Once they have fledged, young swifts are fully independent and are no longer fed by their parents. Fledgling success ranges from 26 to 96 percent.

Both male and female swifts take part in incubating the eggs and feeding the young. Incubation lasts 14 to 32 days. Swifts are altricial and are brooded for 1 to 2 weeks. Chicks stay in the nest for 5 to 8 weeks; nestling growth is highly dependent on the weather since parents have a lower foraging rate in bad weather. Young are fed “food balls” of insects that are held together with saliva; each food ball contains approximately 500 insects. Once chicks fledge, they receive no further parental care. (Campbell and Lack, 1985; Chantler and Driessens, 2000; Chantler, 1999; Collins, 2001; Gill, 1995; )

Behavior

Swifts tend to be social species and will feed and roost in large mixed-species flocks. Most are also colonial breeders, although some are solitary. Roosts of Vaux’s swifts (Chaetura vauxi) in Oregon have been estimated at 20,000 to 30,000 individuals. Roost sites are often traditional. Aerial roosting is known for some species; they maintain their altitude by gliding into the wind, occasionally flapping their wings.

In cold weather, swifts will fluff their feathers and huddle together; sometimes breeding pairs will even roost on top of one another. Nestlings and adults can go into torpor on cold nights.

Most swifts are crepuscular, although nocturnal and diurnal feeding does occur. Active periods vary with weather and usually coincide with insect abundance. On cooler days swifts will leave the roost later or return earlier than on warmer days. If it is particularly cold, they will roost during the day.

Communication and Perception

Swifts communicate acoustically and visually. They are highly vocal; males and females have different calls consisting of chips and rattling or buzzy screams. Males perform aerial displays to attract mates and deter intruders. Sometimes males’ wings will produce sound during aerial displays that is caused by vibrating feathers.

Food Habits

Swifts are insectivores, they catch their prey while in-flight (hawking) or they glean insects from foliage. Swifts drink by flying near the surface of water with an open mouth. They are often crepuscular (feed at dawn or dusk) and roost during the hottest parts of the day, however, there are some nocturnal and diurnal species.

Swifts will often take advantage of swarming insects such as mayflies (Ephemeroptera). They frequently feed on Hymenoptera (bees, wasps and ants), Diptera (true flies), Hemiptera (true bugs) and Coleoptera (beetles). More than 500 prey species have been recorded in Europe alone.

It is possible to find mixed-species flocks (including swallows (Hirundinidae)) feeding together. Niche-separation is facilitated by differences in gape size that correspond with species size and limits the size of prey that can be taken. Elevation can also separate feeding habitats of different species with larger species usually feeding at higher elevations than smaller species. (Campbell and Lack, 1985; Chantler and Driessens, 2000; Collins, 2001; )

Ecosystem Roles

Swifts are hosts to many species of parasite, found on individual birds and in nests. In Africa, parasites include: hippoboscid flies (Gataerina, Pseudolynchia and Ornithomya), feather lice (Dennyus and Eureum) and ticks (Lelaptidae, Proctophyllodiae, Analgesidae and Eustathiidae). Some parasites may have co-evolved with specific species of swifts and are endemic to them.

Economic Importance for Humans: Positive

The edible nests of swiftlets (Collocaliini) are used in bird’s-nest soup, a delicacy in some countries. In 1989, 19,900,000 swiftlet nests were traded globally; they are sold for as much as $1,225 (US)/kg. The swiftlet nest trade is an important part of the economy for many people living in South-east Asia.

It is thought that swift saliva may be used in the development of AIDS treatments as a way to promote cell division in the immune system.

Economic Importance for Humans: Negative

Some species of swift have learned to take advantage of man-made structures as nest sites. For example chimney swifts (Chaetura pelagica) as their name suggests, often nest inside chimneys. This causes problems for those who wish to keep the swifts out, and has led some to cap their chimneys in order to exclude the birds. Generally swifts do not damage the structures, but where they are unwanted, time and money must be spent to keep them out. (Collins, 2001; )

Negative Impacts

household pest

Conservation Status

The IUCN lists no swifts as critically endangered, 1 species as endangered (Guam swiftlet Collocalia bartschi, and 5 species as vulnerable. Populations of other species such as chimney swifts (Chaetura pelagica), white-throated swifts (Aeronautes saxatalis) and black swifts (Cypseloides niger) are declining. Most of the North American species are protected under the Migratory Bird Treaty Act. No swifts are listed by CITES and one species (Mariam gray Aerodramus vanilrorensis bartschi) is listed by ESA.

Threats to swifts include: human disturbance, habitat loss, harvesting of nests, collisions with telephone wires, planes and buildings, pesticides (both those that harm birds directly and others that cause reductions in prey numbers), predation by introduced species (for example cats or snakes) and human induced climate change (since weather has such a large effect on breeding and foraging).

Contributors

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

Neotropical

living in the southern part of the New World. In other words, Central and South America.

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

cooperative breeder

helpers provide assistance in raising young that are not their own

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

crepuscular

active at dawn and dusk

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal

active during the day, 2. lasting for one day.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

Found in northern North America and northern Europe or Asia.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

Disclaimer:
The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.